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In order to obtain an optimum condition of valve lift running with roller followers, in most cases the lobe profile needs to have a concave form (negative radii in the area of the cam lift profile). These negative radii can be less than 50mm. Conventional grinding equipment is not suitable to manufacture this type of cam profile. To avoid these disadvantages, a new type of composite camshaft has been developed. Precision PM lobes are fitted by the thermal shrink fit process to a prepared shaft and as a result no grinding of the lobes is necessary. To avoid lobe grinding, a manufacturing process for the lobes and camshafts was developed, which produces a sufficiently accurate lobe form within the process.

In order to meet requirements for lower fuel consumption, we have developed a technique for significantly decreasing valve train friction for a direct acting OHC engine. Droplets of pure titanium generated by the titanium nitride coating process of the shims improves the surface roughness of the cams, which eliminates the need to polish the cams. In an engine with these shims, the surface roughness of the cams is considerably improved within a few minutes of initial operation by the polishing action of the droplets. Valve train friction is greatly reduced by improving the surface roughness of the cams and shims, which results in better fuel economy.

A novel mechanism using a moving rocker pivot has been developed by Motive Engineering. The chosen approach offers variation of lift, duration, and phase. A compact, robust proof-of-concept mechanism has been designed, and fabricated. It was fitted to the intake valvetrain of a production SOHC four-cylinder engine. The operation of the mechanism is described. A longer-duration, higher-lift camshaft was designed to explore the potential benefits of the concept throughout the speed and load range. Dynamometer testing has been done to explore possible benefits to power, fuel economy, and exhaust emissions.

A pilot production program was initiated to evaluate the suitability of recycled AZ91D magnesium alloy ingot in a production steering column component. Class I A291D magnesium alloy scrap was remelted and refined using an argon flotation technique. The non-metallic inclusion content of the metal was continually monitored by a newly developed light reflectance technique. In addition, chemistry was checked and adjusted to bring the metal into ASTM chemistry specifications. Analysis of the refining operation with respect to cleanliness showed that modifications to the argon gas distribution were necessary. After the necessary modifications were implemented, metal refining efficiency increased. The refined alloy was cast into 11 kg (25 lb.) ingots that were subsequently remelted at Contech's production facility. Parts were produced under the same conditions used for “virgin” metal, and the metal quality was again assessed with the light reflectance technique.

Passenger air bag mounting (PAB) and packaging have been a concern for the Automotive Industry for the last several years. The newer designs of instrument panels are sleeker, smaller and more like fighter plane cock pits. The tighter package size and convoluted instrument panel surfaces require better dimensional control of the air bag mounting locations. The fit and finish of the air bag door is influenced by the position of the air bag housing. The magnesium die cast housing used for the 1996 Chrysler Minivan is one of the keys to the successful seamless passenger door and sweeping I/P surface.

The effect of non-metallic inclusions (NMIs) on the properties of die cast magnesium was investigated. NMI content was quantified by a newly developed light reflectance technique. The mechanical properties of optimized AM60B test bars were found to decrease at high inclusion levels. Low inclusion levels did not statistically reduce the mechanical properties of AM60B as compared to virgin metal. Argon-refined AM60B displayed mechanical properties that were indistinguishable from virgin alloy. AZ91D test plates were die cast at various cleanliness levels. After salt spray testing, it was found that the surface quality of the castings was slightly degraded at high NMI levels. The general corrosion performance was also affected, but paint adhesion was relatively unaffected. At high NMI levels, the corrosion performance was still better than 380 A. Machinability of the AZ91D test plates was quantified by measuring tool wear and cutting forces.

Galvanic corrosion of high purity die cast magnesium alloys AM50 and AZ91 was examined in accelerated atmospheric corrosion testing according to Volvo STD 1027,1375 for 6 weeks involving cycling of the relative humidity between 90% and 45% in combination with intermittent immersion in one of two NaCl-solutions (0.3% or 1.0%). The exposures were performed at two different CO2 levels; 0.01% and 0.3%. The initial general corrosion rate of the AM50 alloy is 50-100% higher than that of AZ91 depending on surface preparation. The corrosion weight loss of both materials depends linearly on salt load in the investigated range. CO2 has a moderate accelerating effect, being higher with decreased salt load. Extreme value analysis was used to evaluate the deepest pit distribution around the perimeter of mounted bolts in panels of AZ91 and AM50. Quite contrary to the general corrosion results, AZ91 showed 30% deeper pits than AM50.

While exhaust gas emission standards are becoming severe, turbochargers which have a good performance and wide operating range are required. At Aisin Seiki, we have started development of the SJ (swirl jet) turbocharger to cope with these requirements without increasing costs. In this paper, we describe the features and effects of the SJ turbocharger.

Optimization of process parameters is critical to minimize the porosity, as well as to maximize the strain at fracture performance of die cast components. In this paper, a two step design of experiments, derived from the Taguchi method, was used to determine the optimum parameter settings for AM60B magnesium die casting alloy. From result analysis, metal temperature and intermediate shot velocity are the most influential parameters for porosity, whereas cavity fill time is the most influential parameter for strain at fracture. Finally, unlike strain at fracture models which are not reproducible, the porosity models are reproducible for both stages of the experiments.

As the use of magnesium continues to grow in the automotive industry, new developments for lightweight driveline components are gaining more interest. Therefore, the need to develop alloys with greater creep resistance and better knowledge of the bolt load behaviour is necessary. Through continuing efforts in research and development, appropriate technical solutions can be found. As a tool in this development work, laboratory test equipment for direct measurements of the bolt load behaviour has been developed based on the use of strain gauged bolts. Bolt load retention behaviour was investigated using Grade 8.8 M8 x 1.25 and M10 x 1.50 standard fasteners which were modified and equipped with strain gauges. The modified fasteners recorded the bolt load during thermal cycling of bolted test specimens of die cast AZ91, AS21 and AE42 magnesium alloys. The test specimens were exposed to various thermal cycles for 100 hours and 500 hours at 125° C and 150° C.

A relatively simple, low-friction Variable-Valve-Actuation (VVA) device is presented. The device can be characterized as a four-bar mechanism consisting of a crank, a rocker and a coupler, all supported on a carrier body. Description of the prototype hardware, and the results of the friction measurements are presented in an accompanying paper [1]. In the present paper, a kinematic analysis/synthesis and a rigid-body dynamic analysis are outlined. Also included is a flexible-body model where the coupler link, which was suspected to be the most severely stressed member, is modeled as a flexible component. A sensitivity-uncertainty analysis employing the Fourier-Amplitude-Sensitivity-Test (FAST) method is conducted to identify the dominant design parameters, and to predict the variations in mechanism's performance due to the uncertainties in the design parameters.

Variable Valve Actuation has been researched and applied to improve engine fuel economy and emissions. The effect on compression release engine retarding has not been considered. Heavy duty diesel engines are recognized for their ability to function as effective vehicle retarders. Many approaches have been taken to convert the power producing diesel engine into a power absorber by altering air flow management. Compression release diesel engine retarding is generated by altering engine valve timing when braking is desired. By releasing the compressed air charge at near TDC compression, the energy absorbed is prevented from returning to the engine during expansion. The net energy loss provides the braking effect. This study discusses the parameters used in system design to achieve maximum performance by using variable valve actuation, VVA, to produce the brake event. Retarding power potential is evaluated by cycle analysis for each system and supported by engine test data.

In this study three EGR methods were applied to a 12 liter turbocharged and intercooled Dl diesel engine, and the exhaust emission and fuel consumption characteristics were compared. One method is the Low Pressure Route system, in which the EGR is taken from down stream of the turbine to the compressor entrance. The other two systems are variations of the High Pressure Route system, in which the EGR is taken from the exhaust manifold to the intake manifold. One of the two High Pressure Route EGR systems is with back pressure valve located at downstream of the turbine and the other uses a variable geometry(VG) turbocharger. It was found that the High Pressure Route EGR system using VG turbocharger was the most effective and practical. With this method the EGR area could be enlarged and NOx reduced by 22% without increase in smoke or fuel consumption while maintaining an adequate excess air ratio.

Variable valve actuation (VVA) has been recognized as a potential method to improve engine efficiency, low-end torque, high-end power, idle stability, and emissions. This paper presents a low-friction VVA device that can modulate the valve lift and timing, and potentially provide many of the benefits listed. In order for the VVA-related additional losses not to out-weigh the benefits, energy consumed in friction and activating the VVA mechanism must be comparable to the total energy consumed by friction in a conventional valvetrain. To confirm this point, hardware was built and installed on a General Motors L-4 cylinder head employing 4 valves per cylinder. The frictional-energy loss and the actuation torque for the mechanism were measured at different speeds and oil temperatures. The dynamometer tests confirmed the simulation results that the mechanism consumes less frictional energy than a direct acting, non-roller type valvetrain.

The new intelligent VVT (Variable Valve Timing) -i, is one of the systems developed to improve engine performance. The pulley unit is one of the most important mechanical components of the system. We developed a suitable process for the four main parts of the VVT-i pulley in order to achieve the target performance at a minimal cost. The requirements for the mechanical component, the pulley unit, include light weight and compact design as well as a quick response time. To satisfy these requirements, we developed three helical gears having unique profiles and high accuracy, and a timing pulley which must prevent pressurized oil from leaking. The inner gear is a helical gear with external teeth,and a key way on its inside diameter. The piston gear is a helical gear of which the inside and outside teeth have opposite helix angles. We developed a unique powder compacting technology for these two gears. The timing pulley is also made of sintered metal alloy.

This paper describes an investigation of a method of implementing VVT with the use of a secondary valve in series with the conventional intake valve of the engine. The secondary valve is not required to withstand the temperatures and pressures of combustion, and therefore can be of relatively lightweight design, so that it is easier to adjust the timing of the secondary valve than that of the main valve. Experiments with such a valve installed in a production engine indicate that benefits of variable valve timing such as overlap optimisation and throttleless load control (4% Fuel benefits at 980 rpm and 1.5 bar IMEP) are attainable with this system.

The paper presents a comparative analysis of the parameters of the injection process in unit injector and pump line nozzle systems. The analysis is based on numerical programs which simulate the working processes of the both systems. The basic assumptions underlying the physical models used in these programs are discussed and the good agreement between numerical results and actual processes is shown. The analysis takes into account the most important parameters for the combustion performance efficiency of injection and durability of the system. The results confirm the essential advantages of unit injection systems for fuelling high-speed diesel engines with direct injection.

This paper describes the application of a variable-phase I.C.R.V. to a modern 4-valve automotive engine with electronic fuel injection and lambda feedback control. Some of the difficulties associated with applying an I.C.R.V. to this kind of engine are discussed. Performance and emissions data are presented for both the baseline (throttled) and I.C.R.V. configurations, and the data compared with predictions from a computer simulation.

A simulation code of an innovative electro-injector for Diesel engines is presented with the preliminary analysis carried out using the code. The simulation code is based on the concentrated volume method. The energy and continuity conservation equations and dynamic equations are used for the movable parts of the system under friction. The one dimensional code simulated the propagation in the feeding pump and the control of the electro-injector. The program uses the method of characteristics to solve conservation equations, simulating the propagation in the pipe between the two chambers. To go deeply into the study of the electro-injector, main routine tests were carried out checking the exact value of diesel fuel parameters and the fuel energy losses with stationary and instationary flows. A comparison with different experimental results obtained by different types of electroinjectors, running at real conditions, has been made with good agreement.

A computer model simulating the flow in fuel injection systems has been used in order to investigate the fuel injection processes in an in-line pump-based fuel injection system for direct-injection diesel engines. The model is one-dimensional and it is based on the mass and momentum conservation equations for the simulation of the fuel flow and on the equilibrium of forces for the simulation of the mechanical movements of the valves present in the system. The fuel injection system tested comprised an in-line pump whose characteristics were examined by using as input the measured line pressure signal and by modeling the pump operation itself as well as the fuel flow through single- and two-stage injectors. For the validation of the model, extensive comparison with experimental data has been performed for a wide range of pump operating conditions.